We display work in progress on a near-infrared tunable
bandpass filter for the wide field camera of the Next
Generation Space Telescope (NGST) Integrated Science
Instrument Module (ISIM). This Demonstration Unit for Low
Order Cryogenic Etalon (DULCE), is designed to demonstrate a
high efficiency scanning Fabry-Perot etalon operating in
interference orders 1-4 at 30 K with a high stability DSP
based servo control system. DULCE has heritage in a Northrop
Grumman system designed for 1st order operation at 300 K,
and is being developed jointly by GSFC and NGC as an option
to satisfy NGST requirements. In this application, scanning
etalons will illuminate the focal plane arrays with a single
order of interference to enable wide field low resolution
(50 << R << 200) hyperspectral imaging over a wide range of
redshifts. We discuss specific science applications that
will be enabled by near-infrared tunable filters.

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